The present generally relates to automatic transmissions. More particularly, the present invention pertains to a clutch device for an automatic transmission.
Generally speaking, an automatic transmission transmits rotational torque from a torque converter disposed on the engine side to a member disposed on the wheel side via a gear train having a carrier, a sun gear, a pinion gear and a ring gear, a brake device and a clutch device. The clutch device transmits the rotational torque from an input member to an output member through engagement of friction plates disposed opposite to each other. Upon disengagement of the friction plates, the clutch device does not transmit rotational torque from the input member to the output member. The engaging or disengaging operation of the clutch device is executed when the shift position of the automatic transmission changes.
FIG. 2 is a cross-sectional view of a known clutch device. The clutch device has an input member 1 forming a wall portion 19 extending toward the outside in the radial direction. An axially extending input drum portion 2 and an axially extending input hub portion 3 are formed on the wall portion 19. The outer edge of each of a plurality of first friction plates 4 is fixed to the inner surface of the input drum portion 2. In addition, the inner edge of each of a plurality of second friction plates 9 is fixed to the outer surface of the input hub portion 3. The input hub portion 3 is surrounded by an output side cylindrical member 6. The output side cylindrical member 6 has a second output portion 7 and an output drum portion 8 extending toward the axial direction. The outer edge of each of a plurality of fourth friction plates 5 is fixed to the inner surface of the output drum portion 8. A first output member 10 is disposed in the inside radial direction of the input drum portion 2. The inner edge of each of a plurality of third friction plates 11 is fixed to the outer surface of the first output member 10. The illustrated clutch device also includes a thrust force receiving plate 12 which receives a thrust force.
The first friction plates 4 and the third friction plates 11 form a first clutch mechanism 13. A first piston 14 is disposed in the input drum portion 2 for effecting engagement of the first friction plates 4 with the third friction plates 11. The first piston 14 is pressed toward the right by a spring 15. The second friction plates 9 and the fourth friction plates 5 form a second clutch mechanism 16. A second piston 17 is disposed inside the output side cylindrical member 6 for effecting engagement of the second friction plates 9 with the fourth friction plates 5. A check valve 18 formed in the second piston 17 discharges centrifugal oil pressure into an oil chamber 17A between the second piston 17 and the output side cylindrical member 6. Therefore, the second clutch mechanism 16 under the engaging condition can be smoothly changed or switched to the disengaging condition.
Another oil chamber 14A is formed between the wall portion 19 and the first piston 14. When oil is supplied to the oil chamber 14A (first oil chamber) by the oil circuit, the first piston 14 moves in the leftward direction in FIG. 2 against the pressing force of the spring 15. Accordingly, the first friction plates 4 engage the third friction plates 11, and the rotational torque of the input member 1 is transmitted to the first output member 10. When the oil in the first oil chamber 14A is discharged, the first friction plates 4 disengage from the third friction plates 11, and the rotational torque of the input member 1 is not transmitted to the first output member 10.
When oil is supplied to the second oil chamber 17A by the oil circuit, the second piston moves toward the left in FIG. 2. Accordingly, the second friction plates 9 engage the fourth friction plates 5, and the rotational torque of the input member 1 is transmitted to the second output member 7. When the oil in the second oil chamber 17A is discharged, the second friction plates 9 are disengaged from the fourth friction plates 5, and the rotational torque of the input member 1 is not transmitted to the second output member 7.
Japanese Laid-Open Publication No. Hei 10-131984 also discloses a clutch device for an automatic transmission in which a first clutch mechanism and a second clutch mechanism are disposed in series in the same axial direction.
However, in the known construction shown in FIG. 2, because the pistons 14, 17 are disposed in series in the axial direction and are moved toward the same direction when the clutch mechanisms 13, 16 are engaged, the length of the clutch device in the axial direction is rather large. Furthermore, because the input member 1 is surrounded by the second output member 7, it is not possible to form a gear on the outer surface of the input member 1.
Japanese Laid-Open Publication No. Hei 11-153152 describes a clutch device for an automatic transmission in which the first clutch mechanism and the second clutch mechanism are disposed on a plane which is perpendicular to the axis of the automatic transmission. In this clutch device, the input member has a wall portion extending toward the outside in the radial direction. A hub portion and a drum portion extending in the axial direction are integrally formed on the wall portion. A first piston is disposed between the hub portion and the wall portion, and a second piston is disposed between the hub portion and the drum portion. With this construction of the clutch device, the structure of the first piston and the second piston is relatively complicated. Furthermore, because the receiving areas of the pistons which receive oil pressure are large, the quantity of oil required to operate the pistons is rather large. Accordingly, the time consumed by the piston operation varies. This can generate shock when the shift position of the automatic transmission is changed.
A need thus exists for a clutch device for an automatic transmission that is not as susceptible to the foregoing drawbacks and disadvantages.
The present invention provides a clutch device for an automatic transmission that includes an input member, a first output member, a second output member, a first clutch mechanism formed between the input member and the first output member, a first piston movable in a first axial direction for engaging the first clutch mechanism to transmit rotation torque from the input member to the first output member by receiving oil pressure, and a second clutch mechanism formed between the input member and the second output member radially outwardly of the first clutch mechanism. The first clutch mechanism and the second clutch mechanism are located in axially overlapping relation to each. A second piston is movable toward the second axial direction that is inverse to the first axial direction for engaging the second clutch mechanism to transmit rotation torque from the input member to the second output member by receiving oil pressure.
According to another aspect of the invention, a clutch device for an automatic transmission includes an input member having an input hub portion and an input drum portion which together establish an annular space, a first output member having a first output drum portion extending in an axial direction in the annular space, a second output member having a second output drum portion disposed between the input drum portion and the first output drum portion and extending in the axial direction in the annular space, a first clutch mechanism for effecting engagement and disengagement between the input hub portion and the first output drum portion, and a second clutch mechanism for effecting engagement and disengagement between the input drum portion and the second output drum portion. A first piston is movable along the inner surface of the first output drum portion for effecting operation of the first clutch mechanism, while a movable second piston is guided by the inner surface of the input drum portion and the outer surface of the input hub portion for effecting operation of the second clutch mechanism. The first and second pistons move in inverse directions to effect engagement of the first and second clutch mechanisms, respectively.
According to another aspect of the invention, an automatic transmission clutch device includes an input member having an input hub portion and an input drum portion, a first output member having a first output drum portion, a second output member having a second output drum portion, a first clutch mechanism for effecting engagement and disengagement between the input hub portion and the first output drum portion, and a second clutch mechanism for effecting engagement and disengagement between the input drum portion and the second output drum portion, with at least a portion of the second clutch mechanism axially overlapping at least a portion of the first clutch mechanism. A movable first piston operable by oil pressure is adapted to effect operation of the first clutch mechanism, and a movable second piston operable by oil pressure is adapted to effect operation of the second clutch mechanism. The first and second pistons move in opposite directions to effect engagement of the first and second clutch mechanisms, respectively.